Prostate cancer accounts for about 230,000 new cancer cases in the USA each year and more than 29,000 men die from it annually. The high mortality rate is attributed to current treatments not providing a cure for hormone-refractory prostate cancer. This project is, therefore, focused on the development of novel tools for highly efficient, precision treatment of metastatic prostate cancer, taking cancer-specific biology into account. It is conceivable that targeting the unique biochemical alterations in prostate cancer cells can be an efficient approach to achieving high therapeutic activity and selectivity. One of the distinctive features of prostate cancer cells, compared to nonmalignant ones, is an excessive cellular level of toxic reactive oxygen species (ROS). These cells have also developed a sophisticated intracellular ROS defense system protecting them against intrinsic oxidative stress. These malignant cells, then, are selectively vulnerable to therapies that further increase ROS level and weaken the ROS defense system. The pilot study found that non-toxic mild hyperthermia (39-40 C) efficiently stimulates ROS generation in metastatic prostate cancer cells and that suppressing one of the key players of the ROS defense system, the DJ-1 gene, significantly increases the toxicity of ROS-induced mild hyperthermia. The goal of the proposed research, therefore, is to develop and test a novel therapeutic modality using the synergetic effect of cancer-targeted mild hyperthermia associated with the suppression of the ROS defense system. To achieve this, and realize a pre-clinical evaluation and clinical application, there is a need to prepare a multi-functional delivery system capable of simultaneously transferring intracellular heaters and DJ-1 siRNA specifically to prostate cancer tumors and non-accessible metastases. The main building block of the delivery system will be magnetic nanoparticles that, when remotely stimulated by an exterior magnetic field, can generate heat from inside cancer cells, while remaining non-toxic to the human body. Moreover, these nanoparticles can simultaneously deliver ROS-resistance suppressors (siRNA) to the cells. Finally, the surface of the nanoparticles will be modified with a hydrophilic polymer (polyethylene glycol, PEG) and cancer-targeting molecules (LHRH peptides), which will prolong the ability of the nanoparticles to circulate through the blood, prevent accumulation in healthy organs, and enhance the delivery targeted at the specific cells. Following intravenous injection, the delivery system will accumulate in prostate cancer cells and the DJ-1 siRNA will inhibit the intracellular ROS defense system. Subsequently, the cancer cells will be remotely heated to a precise temperature by applying a specific-strength external magnetic field. The intracellular hyperthermia will generate the desired ROS level to selectively kill cancer cells. The successful development of the proposed delivery system (Specific Aim 1) and its evaluation on both cancer cells and in mice (Specific Aim 2) will help to assess the potential of this novel approach and to design appropriate steps for its further optimization and assessment.